SUMMARY
Hypoxic ischemic encephalopathy (HIE) is a type of brain disorder or dysfunction that occurs early in life. It is due to a combination of:
- Hypoxia: when brain does not receive enough oxygen for a period of time
- Ischemia: when blood flow to the brain is restricted for a period of time
- Encephalopathy: a brain disorder or dysfunction of the brain
HIE is one type of neonatal encephalopathy (NE). NE is a broad term referring to several brain-related conditions in newborns. NE conditions cause problems in babies’ central nervous systems. The problems begin within the first several days after birth. HIE can happen before birth (during pregnancy), at birth, or immediately after birth. HIE is a relatively rare event, occurring in 2 to 4 of every 1,000 births.
Symptoms and outcomes vary. They depend on the cause and severity of the HIE. Some children experience no health issues. Some have mild to moderate effects. Still others have more severe effects. Severe HIE can cause permanent disability and affect development. It can lead to developmental delay. It can also lead to cerebral palsy, seizures, epilepsy and/or cognitive impairment.
Like the brain, other organs are also dependent on blood supply and oxygen. A reduced blood or oxygen supply can affect these organs, too. For instance, the heart, liver, kidneys, and bowels may be affected alongside the brain. These organs may not function normally. Sometimes, affected organs can recover complete function. However, if the brain sustains injury, it may lead to long-term neurodevelopmental deficits. The duration and severity of the hypoxia and ischemia matter. They determine the severity of any deficits in development and otherwise.
SIGNS AND SYMPTOMS
Symptoms of HIE vary. They depend primarily on the severity of the underlying brain damage. The symptoms can be divided into three types: mild, moderate, and severe.
Mild HIE
Symptoms of mild HIE often resolve within a few weeks. They include:
- Irritability
- Excessive crying or sleeping
- Feeding problems
- Abnormal deep tendon reflexes
- High or stiff muscle tone (hypertonia)
Moderate HIE
Symptoms of moderate HIE include:
- Poor grasp
- Inadequate sucking response
- Low muscle tone (hypotonia), floppiness, or no reflexes
- Episodes of apnea, or stopped breathing
- Seizures in the newborn
Severe HIE
Symptoms of severe HIE include:
- Lack of response to external stimulus
- Severe seizures that cannot be helped with medication
- Irregular or abnormal breathing
- Extreme floppiness (hypotonia)
- Abnormal posturing or body positioning
- Abnormal eye movements
- Abnormal heart rate and blood pressure
- Cardiorespiratory failure
- Other associated organ-injury-related symptoms involving the kidney, liver, and multisystem failure
DIAGNOSIS
HIE is suspected based on:
- Known risk factors
- Pregnancy and labor/birth history
- Medical records from birth documenting fetal:
- Heart rate
- Activity
- Color
- Movements
- Breathing
- Requirements for support and resuscitation around time of birth
To diagnose HIE, a complete physical exam is performed. The medical team examines the baby for symptoms and signs of HIE. Additional labs may help aid the diagnosis. For instance, cord blood tests can help.
Once a diagnosis is suspected, a baby is usually monitored for signs of brain dysfunction. For instance, they may be checked for seizure activity. This is done using an electroencephalogram (EEG). An EEG measures the electrical activity of the brain. Then, continuous video monitoring is used as available. Video helps because signs of seizures may be very subtle and not noticeable in babies.
Magnetic resonance imaging (MRI) is also used. MRI can take pictures of the brain. It can look for signs of brain injury. It can also look for other causes for encephalopathy, such as:
- Stroke
- Hemorrhage (bleeding)
- Brain malformations.
TREATMENT AND THERAPIES
Treatment begins as soon as a diagnosis of HIE is made. This starts in the neonatal intensive care unit (NICU).
Here is what to expect in the NICU:
Brain Cooling
Also known as therapeutic hypothermia.
Therapeutic cooling is the standard of care for HIE. Much research suggests that the extent of brain injury can be reduced when the brain is cooled. It needs to be cooled a few degrees below normal body temperature.
During cooling, the baby is placed on a cooling blanket. The baby’s temperature is closely monitored. The cooling period lasts for three days.
Then the baby is gradually re-warmed to normal temperature.
EEG
Video monitoring
Blood tests
Imaging studies and discussion
When the cooling period is done, the baby will undergo additional imaging studies. Imaging studies take pictures of the brain.
MRI is an important tool that can help assess the extent of brain injury. A pediatric neurologist usually reviews results of MRI, the EEG, and over all clinical course with the family. They will discuss prognosis for the neurodevelopmental outcome.
They will also help plan for long–term follow up care, early intervention, and other supports.
Therapy
Here is what to expect after discharge from the NICU:
Progress checks
OUTLOOK
Outcomes vary depending on the severity of HIE. Some babies do well. They may not have long-lasting effects. Others may require extensive support. They may be intellectually disabled.
Some long-term complications can result from HIE.
They include:
- Developmental delay
- Cerebral palsy
- Intellectual disability
- Seizures
- Hearing and vision problems
- Feeding issues
- Mental health concerns
- Contracture, a tightening of the muscles or other tissues
- Spinal deformities
- Sensory issues
Resources
ORGANIZATIONS/GROUPS
Hope for HIE
The mission of Hope for HIE is to improve the quality of life for children and families impacted by Hypoxic Ischemic Encephalopathy through awareness, education, and support.
Hope for HIE hosts a private Facebook group with over 6,000 members.
PUBLICATIONS
JCN: What Your Pediatric Neurologist Wants You to Know: Neonatal Neurology
Podcast from SAGE Neuroscience and Neurology/Journal of Child Neurology (JCN). JCN’s Residents and Fellows Board Director, Dr. Alison Christy, interviews Dr. Sonika Agarwal, a neonatal neurologist from Children’s Hospital in Philadelphia.
Child Neurology Foundation (CNF) solicits resources from the community to be included on this webpage through an application process. CNF reserves the right to remove entities at any time if information is deemed inappropriate or inconsistent with the mission, vision, and values of CNF.